Multi-station document inserting systems generally include a plurality of various stations configured for specific applications. Such machines are known in the art and are generally used by organizations, which produce a large volume of mailings where the content of each mail piece may vary.
In a typical envelope insertion machine for mass mailing, there is a gathering section where the enclosure material is gathered before it is inserted into an envelope. This gathering section includes a gathering transport with pusher fingers rigidly attached to a conveying means and a plurality of enclosure feeders mounted above the transport. If the enclosure material contains many documents, these documents are separately fed by different enclosure feeders. After all the released documents are gathered, they are put into a stack to be inserted into an envelope in an inserting station.
At the same time, envelopes are sequentially fed to the inserting station, and each envelope is placed on a platform with its flap flipped back all the way, so that a plurality of mechanical fingers or a vacuum suction device can keep the envelope on the platform while the throat of the envelope is pulled away to open the envelope.
Before envelopes are fed to the insertion station, they are usually supplied in a stack in a supply tray or envelope hopper. Envelopes are then separated by an envelope feeder so that only one envelope is fed to the insertion station at a time. For that reason, an envelope feeder is also referred to as an envelope singulator. In a high-speed insertion machine, the feeder should be able to feed single envelopes at a rate of approximately 18,000 No. 10 envelopes per hour. At this feeding rate, it is critical that only a single envelope at a time is picked up and delivered to the insertion station.
However, deformed envelopes (cupped or twisted) degrade performance of the feeder. Such deformation can result in slippage that causes the envelopes to be fed too slowly. Slippage may also result, for example, from insufficient pressure on the envelope stack, or from envelopes made from a material that has low friction. A prior solution to this problem involved using a suction cup to assist in feeding the envelopes. However, constant use of the suction cup involves additional risks of misfeeds and jams.
At a feeding period approximately equal to 200 ms, there are roughly 30 ms available for the feeder to reset before the next feed cycle is initiated. If an envelope is not present in close proximity before the next feed time, acquisition of the next envelope will not occur and a feed cycle will be missed, resulting in a reduced machine throughput.
Known envelope feeder systems for an inserter system are described in U.S. Pat. No. 6,250,625, Method for Supplying Envelopes to an Inserter System by Way of Multiple Paths, and U.S. Pat. No. 6,425,579, Low Friction Envelope Feeder, which are hereby incorporated by reference.